Gadget Testing¶
This file summarizes information on basic testing of USB functions provided by gadgets.
1. ACM function¶
The function is provided by usb_f_acm.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “acm”. The ACM function provides just one attribute in its function directory:
port_num
The attribute is read-only.
There can be at most 4 ACM/generic serial/OBEX ports in the system.
Testing the ACM function¶
On the host:
cat > /dev/ttyACM<X>
On the device:
cat /dev/ttyGS<Y>
then the other way round
On the device:
cat > /dev/ttyGS<Y>
On the host:
cat /dev/ttyACM<X>
2. ECM function¶
The function is provided by usb_f_ecm.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “ecm”. The ECM function provides these attributes in its function directory:
ifname
network device interface name associated with this function instance
qmult
queue length multiplier for high and super speed
host_addr
MAC address of host’s end of this Ethernet over USB link
dev_addr
MAC address of device’s end of this Ethernet over USB link
and after creating the functions/ecm.<instance name> they contain default values: qmult is 5, dev_addr and host_addr are randomly selected. Except for ifname they can be written to until the function is linked to a configuration. The ifname is read-only and contains the name of the interface which was assigned by the net core, e. g. usb0.
Testing the ECM function¶
Configure IP addresses of the device and the host. Then:
On the device:
ping <host's IP>
On the host:
ping <device's IP>
3. ECM subset function¶
The function is provided by usb_f_ecm_subset.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “geth”. The ECM subset function provides these attributes in its function directory:
ifname
network device interface name associated with this function instance
qmult
queue length multiplier for high and super speed
host_addr
MAC address of host’s end of this Ethernet over USB link
dev_addr
MAC address of device’s end of this Ethernet over USB link
and after creating the functions/ecm.<instance name> they contain default values: qmult is 5, dev_addr and host_addr are randomly selected. Except for ifname they can be written to until the function is linked to a configuration. The ifname is read-only and contains the name of the interface which was assigned by the net core, e. g. usb0.
Testing the ECM subset function¶
Configure IP addresses of the device and the host. Then:
On the device:
ping <host's IP>
On the host:
ping <device's IP>
4. EEM function¶
The function is provided by usb_f_eem.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “eem”. The EEM function provides these attributes in its function directory:
ifname
network device interface name associated with this function instance
qmult
queue length multiplier for high and super speed
host_addr
MAC address of host’s end of this Ethernet over USB link
dev_addr
MAC address of device’s end of this Ethernet over USB link
and after creating the functions/eem.<instance name> they contain default values: qmult is 5, dev_addr and host_addr are randomly selected. Except for ifname they can be written to until the function is linked to a configuration. The ifname is read-only and contains the name of the interface which was assigned by the net core, e. g. usb0.
Testing the EEM function¶
Configure IP addresses of the device and the host. Then:
On the device:
ping <host's IP>
On the host:
ping <device's IP>
5. FFS function¶
The function is provided by usb_f_fs.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “ffs”. The function directory is intentionally empty and not modifiable.
After creating the directory there is a new instance (a “device”) of FunctionFS available in the system. Once a “device” is available, the user should follow the standard procedure for using FunctionFS (mount it, run the userspace process which implements the function proper). The gadget should be enabled by writing a suitable string to usb_gadget/<gadget>/UDC.
Testing the FFS function¶
On the device: start the function’s userspace daemon, enable the gadget
On the host: use the USB function provided by the device
6. HID function¶
The function is provided by usb_f_hid.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “hid”. The HID function provides these attributes in its function directory:
protocol
HID protocol to use
report_desc
data to be used in HID reports, except data passed with /dev/hidg<X>
report_length
HID report length
subclass
HID subclass to use
For a keyboard the protocol and the subclass are 1, the report_length is 8, while the report_desc is:
$ hd my_report_desc
00000000 05 01 09 06 a1 01 05 07 19 e0 29 e7 15 00 25 01 |..........)...%.|
00000010 75 01 95 08 81 02 95 01 75 08 81 03 95 05 75 01 |u.......u.....u.|
00000020 05 08 19 01 29 05 91 02 95 01 75 03 91 03 95 06 |....).....u.....|
00000030 75 08 15 00 25 65 05 07 19 00 29 65 81 00 c0 |u...%e....)e...|
0000003f
Such a sequence of bytes can be stored to the attribute with echo:
$ echo -ne \\x05\\x01\\x09\\x06\\xa1.....
Testing the HID function¶
Device:
create the gadget
connect the gadget to a host, preferably not the one used to control the gadget
run a program which writes to /dev/hidg<N>, e.g. a userspace program found in Documentation/usb/gadget_hid.rst:
$ ./hid_gadget_test /dev/hidg0 keyboard
Host:
observe the keystrokes from the gadget
7. LOOPBACK function¶
The function is provided by usb_f_ss_lb.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “Loopback”. The LOOPBACK function provides these attributes in its function directory:
qlen
depth of loopback queue
bulk_buflen
buffer length
Testing the LOOPBACK function¶
device: run the gadget
host: test-usb (tools/usb/testusb.c)
8. MASS STORAGE function¶
The function is provided by usb_f_mass_storage.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “mass_storage”. The MASS STORAGE function provides these attributes in its directory: files:
stall
Set to permit function to halt bulk endpoints. Disabled on some USB devices known not to work correctly. You should set it to true.
num_buffers
Number of pipeline buffers. Valid numbers are 2..4. Available only if CONFIG_USB_GADGET_DEBUG_FILES is set.
and a default lun.0 directory corresponding to SCSI LUN #0.
A new lun can be added with mkdir:
$ mkdir functions/mass_storage.0/partition.5
Lun numbering does not have to be continuous, except for lun #0 which is created by default. A maximum of 8 luns can be specified and they all must be named following the <name>.<number> scheme. The numbers can be 0..8. Probably a good convention is to name the luns “lun.<number>”, although it is not mandatory.
In each lun directory there are the following attribute files:
file
The path to the backing file for the LUN. Required if LUN is not marked as removable.
ro
Flag specifying access to the LUN shall be read-only. This is implied if CD-ROM emulation is enabled as well as when it was impossible to open “filename” in R/W mode.
removable
Flag specifying that LUN shall be indicated as being removable.
cdrom
Flag specifying that LUN shall be reported as being a CD-ROM.
nofua
Flag specifying that FUA flag in SCSI WRITE(10,12)
Testing the MASS STORAGE function¶
device: connect the gadget, enable it host: dmesg, see the USB drives appear (if system configured to automatically mount)
9. MIDI function¶
The function is provided by usb_f_midi.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “midi”. The MIDI function provides these attributes in its function directory:
buflen
MIDI buffer length
id
ID string for the USB MIDI adapter
in_ports
number of MIDI input ports
index
index value for the USB MIDI adapter
out_ports
number of MIDI output ports
qlen
USB read request queue length
Testing the MIDI function¶
There are two cases: playing a mid from the gadget to the host and playing a mid from the host to the gadget.
Playing a mid from the gadget to the host:
host:
$ arecordmidi -l
Port Client name Port name
14:0 Midi Through Midi Through Port-0
24:0 MIDI Gadget MIDI Gadget MIDI 1
$ arecordmidi -p 24:0 from_gadget.mid
gadget:
$ aplaymidi -l
Port Client name Port name
20:0 f_midi f_midi
$ aplaymidi -p 20:0 to_host.mid
Playing a mid from the host to the gadget
gadget:
$ arecordmidi -l
Port Client name Port name
20:0 f_midi f_midi
$ arecordmidi -p 20:0 from_host.mid
host:
$ aplaymidi -l
Port Client name Port name
14:0 Midi Through Midi Through Port-0
24:0 MIDI Gadget MIDI Gadget MIDI 1
$ aplaymidi -p24:0 to_gadget.mid
The from_gadget.mid should sound identical to the to_host.mid.
The from_host.id should sound identical to the to_gadget.mid.
MIDI files can be played to speakers/headphones with e.g. timidity installed:
$ aplaymidi -l
Port Client name Port name
14:0 Midi Through Midi Through Port-0
24:0 MIDI Gadget MIDI Gadget MIDI 1
128:0 TiMidity TiMidity port 0
128:1 TiMidity TiMidity port 1
128:2 TiMidity TiMidity port 2
128:3 TiMidity TiMidity port 3
$ aplaymidi -p 128:0 file.mid
MIDI ports can be logically connected using the aconnect utility, e.g.:
$ aconnect 24:0 128:0 # try it on the host
After the gadget’s MIDI port is connected to timidity’s MIDI port, whatever is played at the gadget side with aplaymidi -l is audible in host’s speakers/headphones.
10. NCM function¶
The function is provided by usb_f_ncm.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “ncm”. The NCM function provides these attributes in its function directory:
ifname
network device interface name associated with this function instance
qmult
queue length multiplier for high and super speed
host_addr
MAC address of host’s end of this Ethernet over USB link
dev_addr
MAC address of device’s end of this Ethernet over USB link
and after creating the functions/ncm.<instance name> they contain default values: qmult is 5, dev_addr and host_addr are randomly selected. Except for ifname they can be written to until the function is linked to a configuration. The ifname is read-only and contains the name of the interface which was assigned by the net core, e. g. usb0.
Testing the NCM function¶
Configure IP addresses of the device and the host. Then:
On the device:
ping <host's IP>
On the host:
ping <device's IP>
11. OBEX function¶
The function is provided by usb_f_obex.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “obex”. The OBEX function provides just one attribute in its function directory:
port_num
The attribute is read-only.
There can be at most 4 ACM/generic serial/OBEX ports in the system.
Testing the OBEX function¶
On device:
seriald -f /dev/ttyGS<Y> -s 1024
On host:
serialc -v <vendorID> -p <productID> -i<interface#> -a1 -s1024 \
-t<out endpoint addr> -r<in endpoint addr>
where seriald and serialc are Felipe’s utilities found here:
12. PHONET function¶
The function is provided by usb_f_phonet.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “phonet”. The PHONET function provides just one attribute in its function directory:
ifname
network device interface name associated with this function instance
Testing the PHONET function¶
It is not possible to test the SOCK_STREAM protocol without a specific piece of hardware, so only SOCK_DGRAM has been tested. For the latter to work, in the past I had to apply the patch mentioned here:
http://www.spinics.net/lists/linux-usb/msg85689.html
These tools are required:
git://git.gitorious.org/meego-cellular/phonet-utils.git
On the host:
$ ./phonet -a 0x10 -i usbpn0
$ ./pnroute add 0x6c usbpn0
$./pnroute add 0x10 usbpn0
$ ifconfig usbpn0 up
On the device:
$ ./phonet -a 0x6c -i upnlink0
$ ./pnroute add 0x10 upnlink0
$ ifconfig upnlink0 up
Then a test program can be used:
http://www.spinics.net/lists/linux-usb/msg85690.html
On the device:
$ ./pnxmit -a 0x6c -r
On the host:
$ ./pnxmit -a 0x10 -s 0x6c
As a result some data should be sent from host to device. Then the other way round:
On the host:
$ ./pnxmit -a 0x10 -r
On the device:
$ ./pnxmit -a 0x6c -s 0x10
13. RNDIS function¶
The function is provided by usb_f_rndis.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “rndis”. The RNDIS function provides these attributes in its function directory:
ifname
network device interface name associated with this function instance
qmult
queue length multiplier for high and super speed
host_addr
MAC address of host’s end of this Ethernet over USB link
dev_addr
MAC address of device’s end of this Ethernet over USB link
and after creating the functions/rndis.<instance name> they contain default values: qmult is 5, dev_addr and host_addr are randomly selected. Except for ifname they can be written to until the function is linked to a configuration. The ifname is read-only and contains the name of the interface which was assigned by the net core, e. g. usb0.
Testing the RNDIS function¶
Configure IP addresses of the device and the host. Then:
On the device:
ping <host's IP>
On the host:
ping <device's IP>
14. SERIAL function¶
The function is provided by usb_f_gser.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “gser”. The SERIAL function provides just one attribute in its function directory:
port_num
The attribute is read-only.
There can be at most 4 ACM/generic serial/OBEX ports in the system.
Testing the SERIAL function¶
On host:
insmod usbserial
echo VID PID >/sys/bus/usb-serial/drivers/generic/new_id
On host:
cat > /dev/ttyUSB<X>
On target:
cat /dev/ttyGS<Y>
then the other way round
On target:
cat > /dev/ttyGS<Y>
On host:
cat /dev/ttyUSB<X>
15. SOURCESINK function¶
The function is provided by usb_f_ss_lb.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “SourceSink”. The SOURCESINK function provides these attributes in its function directory:
pattern
0 (all zeros), 1 (mod63), 2 (none)
isoc_interval
1..16
isoc_maxpacket
0 - 1023 (fs), 0 - 1024 (hs/ss)
isoc_mult
0..2 (hs/ss only)
isoc_maxburst
0..15 (ss only)
bulk_buflen
buffer length
bulk_qlen
depth of queue for bulk
iso_qlen
depth of queue for iso
Testing the SOURCESINK function¶
device: run the gadget
host: test-usb (tools/usb/testusb.c)
16. UAC1 function (legacy implementation)¶
The function is provided by usb_f_uac1_legacy.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “uac1_legacy”. The uac1 function provides these attributes in its function directory:
audio_buf_size
audio buffer size
fn_cap
capture pcm device file name
fn_cntl
control device file name
fn_play
playback pcm device file name
req_buf_size
ISO OUT endpoint request buffer size
req_count
ISO OUT endpoint request count
The attributes have sane default values.
Testing the UAC1 function¶
device: run the gadget
host:
aplay -l # should list our USB Audio Gadget
17. UAC2 function¶
The function is provided by usb_f_uac2.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “uac2”. The uac2 function provides these attributes in its function directory:
c_chmask
capture channel mask
c_srate
capture sampling rate
c_ssize
capture sample size (bytes)
p_chmask
playback channel mask
p_srate
playback sampling rate
p_ssize
playback sample size (bytes)
req_number
the number of pre-allocated request for both capture and playback
The attributes have sane default values.
Testing the UAC2 function¶
device: run the gadget host: aplay -l # should list our USB Audio Gadget
This function does not require real hardware support, it just sends a stream of audio data to/from the host. In order to actually hear something at the device side, a command similar to this must be used at the device side:
$ arecord -f dat -t wav -D hw:2,0 | aplay -D hw:0,0 &
e.g.:
$ arecord -f dat -t wav -D hw:CARD=UAC2Gadget,DEV=0 | \
aplay -D default:CARD=OdroidU3
18. UVC function¶
The function is provided by usb_f_uvc.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “uvc”. The uvc function provides these attributes in its function directory:
streaming_interval
interval for polling endpoint for data transfers
streaming_maxburst
bMaxBurst for super speed companion descriptor
streaming_maxpacket
maximum packet size this endpoint is capable of sending or receiving when this configuration is selected
There are also “control” and “streaming” subdirectories, each of which contain a number of their subdirectories. There are some sane defaults provided, but the user must provide the following:
control header
create in control/header, link from control/class/fs and/or control/class/ss
streaming header
create in streaming/header, link from streaming/class/fs and/or streaming/class/hs and/or streaming/class/ss
format description
create in streaming/mjpeg and/or streaming/uncompressed
frame description
create in streaming/mjpeg/<format> and/or in streaming/uncompressed/<format>
Each frame description contains frame interval specification, and each such specification consists of a number of lines with an inverval value in each line. The rules stated above are best illustrated with an example:
# mkdir functions/uvc.usb0/control/header/h
# cd functions/uvc.usb0/control/
# ln -s header/h class/fs
# ln -s header/h class/ss
# mkdir -p functions/uvc.usb0/streaming/uncompressed/u/360p
# cat <<EOF > functions/uvc.usb0/streaming/uncompressed/u/360p/dwFrameInterval
666666
1000000
5000000
EOF
# cd $GADGET_CONFIGFS_ROOT
# mkdir functions/uvc.usb0/streaming/header/h
# cd functions/uvc.usb0/streaming/header/h
# ln -s ../../uncompressed/u
# cd ../../class/fs
# ln -s ../../header/h
# cd ../../class/hs
# ln -s ../../header/h
# cd ../../class/ss
# ln -s ../../header/h
Testing the UVC function¶
device: run the gadget, modprobe vivid:
# uvc-gadget -u /dev/video<uvc video node #> -v /dev/video<vivid video node #>
- where uvc-gadget is this program:
with these patches:
host:
luvcview -f yuv
19. PRINTER function¶
The function is provided by usb_f_printer.ko module.
Function-specific configfs interface¶
The function name to use when creating the function directory is “printer”. The printer function provides these attributes in its function directory:
pnp_string
Data to be passed to the host in pnp string
q_len
Number of requests per endpoint
Testing the PRINTER function¶
The most basic testing:
device: run the gadget:
# ls -l /devices/virtual/usb_printer_gadget/
should show g_printer<number>.
If udev is active, then /dev/g_printer<number> should appear automatically.
host:
If udev is active, then e.g. /dev/usb/lp0 should appear.
host->device transmission:
device:
# cat /dev/g_printer<number>
host:
# cat > /dev/usb/lp0
device->host transmission:
# cat > /dev/g_printer<number>
host:
# cat /dev/usb/lp0
More advanced testing can be done with the prn_example described in Documentation/usb/gadget_printer.rst.
20. UAC1 function (virtual ALSA card, using u_audio API)¶
The function is provided by usb_f_uac1.ko module. It will create a virtual ALSA card and the audio streams are simply sinked to and sourced from it.
Function-specific configfs interface¶
The function name to use when creating the function directory is “uac1”. The uac1 function provides these attributes in its function directory:
c_chmask
capture channel mask
c_srate
capture sampling rate
c_ssize
capture sample size (bytes)
p_chmask
playback channel mask
p_srate
playback sampling rate
p_ssize
playback sample size (bytes)
req_number
the number of pre-allocated request for both capture and playback
The attributes have sane default values.
Testing the UAC1 function¶
device: run the gadget host: aplay -l # should list our USB Audio Gadget
This function does not require real hardware support, it just sends a stream of audio data to/from the host. In order to actually hear something at the device side, a command similar to this must be used at the device side:
$ arecord -f dat -t wav -D hw:2,0 | aplay -D hw:0,0 &
e.g.:
$ arecord -f dat -t wav -D hw:CARD=UAC1Gadget,DEV=0 | \
aplay -D default:CARD=OdroidU3